论文标题:典型海域海底底床稳定性研究
Seabed Stability Research of Typical Sea Areas
论文作者
论文导师 阎军；林缅,论文学位 博士,论文专业 海洋地质
论文单位 中国科学院研究生院（海洋研究所）,点击次数 125,论文页数 103页File Size10199K
2007-05-01论文网 http://www.lw23.com/lunwen_3094602/
Huiquan Bay;grain size trend analysis;Beibu Gulf;sand wave;multi-beam bathymetric system;sand transportation
随着对海洋资源的开发,大量的海底工程设施应运而生,而对其依托的海底底床稳定性的研究就成为海洋地质和海洋工程学者当务之急的工作重点之一。不同的地质单元受控的海洋环境差异很大,海底底床的稳定性也表现出不同的特点,为此,针对不同的地质单元就需要选用不同的分析方法。本文选取以海底沙坝与海槽为主要地貌单元的青岛市汇泉湾海水浴场,以及沙脊和沙波广泛发育的南海北部湾西南海域浅海陆架两个典型海域作为研究区域。对于潮流和波浪碎裂流控制的海水浴场,通过采集表层样,借助流速仪、全站仪、激光粒度仪、DGPS定位,利用粒径趋势分析模型GSTA(Gao S,1996),结合地形测量数据和潮流数据,分析了海水浴场的表层沉积物粒度特征、沉积物类型、冲淤变化及输运方向;而对波浪潮流联合作用的北部湾西南浅海陆架采用多波束测深系统、DGPS定位等仪器测量手段,利用图像对比方法结合泥沙输运模型SEDTRANS(Michael Li, 2001),分析浅海陆架海底底床的地貌特点、地质单元类型、沙波底床的输运速率和方向、冲淤变化及底床稳定性对海底管线安全的影响。 采集并分析了青岛市汇泉湾海水浴场149个表层样品的粒度参数特征,结合沉积物输运趋势分析模型结果和水动力观测资料得出高潮线到沙坝沉积物输运方向为SE向,沙坝向海一翼沉积物输运方向为NW向;地形测量数据显示侵蚀区域主要分布在3月份沙坝脊线附近,而3月份槽线附近为主要的堆积区。 对比分析北部湾西南部海区2004～2006连续3年的多波束海底地貌扫描数据,得出研究区域海底沙波的波长为5.8～91.8m,波高0.1～4.3m,陡峭度0.013～0.12,对称指数0.32～6.52。沙波的移动速率最大达48.8m/a,移动方向在研究区域西部为SE向,中部呈往复迁移,东部为NW向;沙波不同部位的迁移速率不同,一般的沙波尾翼迁移速率较大;同一组沙波存在反向扭转迁移的现象,反向扭转迁移的轴线位于研究区域沙脊的脊线附近,这种反向迁移不仅与底层流作用有关,还与海底地形关系密切;04～06年西部海底底床处于侵蚀状态,局部的最大侵蚀量可达1.3m,东部处于堆积状态,最大堆积量达2.8m。 对于发育沙坝-海槽型潮上带和潮间带,粒径趋势分析模型结合地形测量以及水动力测量,分析底床冲淤变化及泥沙搬运方向,具有省时省力高效的优点,同时很好的弥补了粒径趋势分析模型对冲淤量的预测无能为力这一缺陷;对于沙脊沙波广泛发育的浅海陆架,通过对比多年的沙波地貌图计算沙波的迁移速率和方向,避开了通过潮流场模型预测沙波活动,因考虑底床稳定性的控制因素不足而带来的误差,为评价沙脊沙波型底床的稳定性提供新的可行性研究方法。
With marine resources explored, large numbers of marine engineering establishments are built. The marine geologists and the engineers focus on the research of seabed stability, on which the constructions are based. However in various marine environments, the seabed stability has different characters, and then collecting corresponding analytic methods are required in various geologic regions. Sand-bar and trough system in Huiquan Bay Beach in Qingdao, and sand ridges and sand waves in southeast Beibu Gulf are systemically researched in the thesis. Based on the analysis of surficial sediments, grain size trend analysis model, topographic and tidal current velocity measures are combined in Huiquan Bay Beach to analyze surficial sediment distribution pattern, transportation trend, transportation direction, deposition and erosion of the beach. Based on the use of bathymetric instruments and DGPS system, the relief patterns and geology regions are identified clearly. Relief maps of three years are compared to get migration velocity, and direction of sand waves, and deposition and erosion in the seabed. In the end, the effect on the submarine pipelines of seabed stability is discussed. 149 surficial sediment samples were collected and analyzed over Huiquan Beach of Qingdao. In combination with hydrodynamic measures, surficial sediment distribution pattern and transportation trend of the beach are analyzed. It shows that there is a close relationship between the distribution pattern of sediment grain size and hydrodynamic conditions. The fine sands are transported towards east along shoreline driven by the alongshore current, while the coarse sands remain at the original position. The sediment sortation results in an ordinal pattern characterized by fine gravels, coarse sands, medium sands and fine sands from northwest to southeast in the area. In addition, the surficial sediment types are closely consistent with the mean grain size distribution. In Huiquan Bay Beach, the sediments are transported towards southeast from the high tide line to the sandbar, while towards northwest from the crest of sand bar to its offshore flank. Topographic measures show that the erosion area is distributed mostly near the crest of sand bar in March with the erosion volume up to 656.17m3. But in the same period, area near the trough is the main depocenter with the deposition volume up to 12415.96m3. Tidal current velocity and topography measures validate the results of grain size trend analysis and make up the disadvantages of grain trend size analysis in predicting erosion and deposition. Sand wave migration has an important effect on the seabed stability. Using multi-beam system, repetitive seabed micro-geomorphologic measures from 2004 to 2006 are analyzed. The investigated results show that the wavelength of sand wave ranges from 5.8 to 91.8m, wave height from 0.1 to 4.3, steepness from 0.013 to 0.12, and symmetry from 0.32 to 6.52. The sand wave migration velocity is up to 48.8m/a, migration direction is oriented SE in the west of the researched area, NW in the east, and to and fro in the mid. The migration velocity varies in different sections, and commonly the end of the sand wave migrates more rapidly. Reverse migration exists in a set of sand waves, and the axis line locates near the crest of the sand ridge, upon which the sand waves are superimposed, indicating that the reverse migration is not only related to bottom current but also to submarine topography. From 2004 to 2006, the seabed is under erosion, in the west and the erosion is up to 1.3m, while the seabed is under deposition, in the east, and the deposition is up to 2.8m. In the supralittoral zone and intertidal zone, in which sand-bar and trough system is developed, grain size trend analysis model, topographic and tidal current velocity measures are combined in Huiquan Bay Beach to do seabed erosion and deposition analysis. The results show the method makes up the disadvantages of grain trend size analysis in predicting erosion and deposition. In the shelf, on which sand ridges and sand waves is widely developed, three years relief maps are compared to get migration velocity and direction of sand waves. This technique is feasible in researching seabed stability, such as movement of sand waves.
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